The present invention relates to cushion members adapted for use in seats of vehicles, such as automobiles, vessels, aircraft, etc., or in some pieces of furniture, such as sofas, beds, etc., and a method and an apparatus for manufacturing the same.
Conventionally, synthetic resin foam, such as polyurethane foam, has been used for many of cushion members that are employed in seats of vehicles, for example. Described in U.S. Pat. No. 5,639,543 is a cushion member with a three-dimensional network structure that is formed of a thermoplastic resin. This cushion member has been proposed to ensure higher breathability or to facilitate re-fusion for recycling.
In order to manufacture the cushion member with the network structure, a large number of continuous fibers that can be obtained by discharging a molten thermoplastic resin through a number of nozzles are guided between a pair of flat conveyor belts, right and left, into a cooling tank. A cushion member (network block) in the shape of a rectangular parallelepiped can be obtained by looping these continuous filaments in the cooling tank and bonding the respective contact portions of the resulting loops.
In order to give a desired cushion member shape to the network block, the block is put in a forming mold and hot-pressed, conventionally. By this hot pressing, the network block is compressed so that its volume is substantially halved, and is molded into the desired shape. Thereupon, the cushion member can acquire its final product shape.
In the case where the network block is compressed by hot pressing, its apparent density (or weight) increases unduly. Further, this block forming method requires many man-hours and long operating time, thus entailing high cost.
Accordingly, the object of the present invention is to provide a cushion member and an apparatus for manufacturing the same, whereby a cushion member having a three-dimensional network structure with a desired shape can be manufactured efficiently without entailing substantial compression.
In order to achieve the above object, a cushion member according to the present invention comprises a three-dimensional network structure with an apparent density of 0.005 to 0.20 g/cm3, formed by looping a plurality of continuous filaments of a thermoplastic resin with fineness of 300 to 100,000 deniers and bonding the respective contact portions of the filaments, the network structure being solidified in a manner such that the continuous filaments are moved inward from opposite surfaces in the thickness direction of the cushion member to be formed and from opposite sides, depending on the product shape of the cushion member, as the continuous filaments are looped.
The cushion member of the invention constructed in this manner does not require use of a binder and is formed of thermoplastic resin (preferably, thermoplastic elastic resin), so that it can be refused to be recycled. As the continuous filaments are delivered from nozzles and looped, the cushion member acquires a shape that resembles its final product shape. Thus, the product shape can be obtained without requiring substantial compression, so that the density of the structure cannot be too high to secure lightness in weight. The cushion member of the invention has high breathability and fatigue resistance, and can be finished with a low degree of compression for secondary forming, so that it is light in weight. Since the continuous filaments are looped between the opposite sides of the cushion member, moreover, the cushion member can enjoy better cushioning characteristics.
A manufacturing method for a cushion member according to the invention comprises a process for discharging a softened thermoplastic resin through a plurality of nozzles, thereby looping a plurality of continuous filaments and bonding the respective contact portions of the filaments, and a process for solidifying the continuous filaments in a manner such that the filaments are moved inward from opposite surfaces in the thickness direction of the cushion member to be formed and from opposite sides by means of guide means having shaping guide surfaces corresponding to the outline of the profile of the cushion member as the filaments are looped. This manufacturing method lowers or obviates the necessity of a post-process (secondary forming process), such as a compression process, for giving the final product shape to the cushion member. According to this manufacturing method, the three-dimensional cushion member with a network structure can be continuously manufactured with high efficiency, and the final product shape can be finished without requiring substantial compression for secondary forming. In some cases, the secondary forming process can be omitted. Accordingly, the manufacturing cost can be lowered, and a cushion member with high durability and breathability can be obtained without suffering too high a density.
The manufacturing method of the invention may further comprise a process for additionally forming the cushion member in a manner such that the cushion member is held from both sides thereof by means of a secondary forming mold while the temperature of the cushion member, delivered continuously from the guide means, is within a range for thermal deformation. The secondary forming operation can accurately finish the cushion member in its final product shape. Since the cushion member can be preformed into a shape that resembles the shape of a finished product before it is secondary formed, moreover, the secondary forming operation requires only a low degree of compression.
A cushion manufacturing apparatus according to the invention comprises a nozzle portion having a plurality of nozzles for continuously discharging a softened thermoplastic resin, whereby a plurality of continuous filaments discharged from the nozzles are looped with the respective contact portions thereof bonded together, guide means located under the nozzle portion and having shaping guide surfaces corresponding to the outline of the profile of the cushion member to be formed, the guide means serving to move the continuous filaments inward from opposite surfaces in the thickness direction of the cushion member and from opposite sides as the filaments are looped, and cooling means for cooling the continuous filaments, thereby solidifying the same. According to this manufacturing apparatus, the cushion member can be preformed as the continuous filaments are looped (or when the network structure is manufactured), the subsequent secondary forming process (for finishing into the final product shape) requires only a low degree of compression. Thus, the three-dimensional cushion member with a network structure can be continuously manufactured with high efficiency.
In the cushion manufacturing apparatus of the invention, the guide means may include a pair of first guide portions opposed individually to the thickness direction opposite surfaces of the cushion member to be formed and a pair of second guide members opposed to the opposite sides of the cushion member to be formed, the first and second guide portions including a plurality of rollers individually having outer peripheral surfaces corresponding to the outline of the profile of the cushion member and belts stretched between the rollers and capable of endlessly running to change the respective shapes thereof depending on the respective shapes of the outer peripheral surfaces of the rollers, thereby forming the shaping guide surfaces. With use of this guide means that holds the cushion member in the four directions, the unsolidified network structure can be preformed so that its shape resembles the final product shape of the cushion member. According to this manufacturing apparatus, the network structure is moved from the four sides by means of the first and second guide portions, so that it can be shaped further effectively.
In the cushion manufacturing apparatus of the invention, the guide means may include a pair of guide portions opposed to each other across the cushion member to be formed, the guide portions including a plurality of rollers individually having outer peripheral surfaces surrounding the thickness-direction opposite surfaces and the opposite sides of the cushion member and belts stretched between the rollers and capable of endlessly running to change the respective shapes thereof depending on the respective shapes of the outer peripheral surfaces of the rollers, thereby forming the shaping guide surfaces. Also with use of this guide means that holds the cushion member in the two directions, the unsolidified network structure can be formed so that its shape resembles the final product shape of the cushion member. According to this manufacturing apparatus, the number of rollers that constitute the guide means can be reduced.
In the cushion manufacturing apparatus of the invention, the guide means may be designed so that the distance of movement of the continuous filaments from the opposite sides is greater than the distance of movement in the thickness direction of the cushion member. According to this manufacturing apparatus, the continuous filaments can be looped in the thickness direction of the cushion member between the opposite sides thereof, so that the cushioning characteristics of the cushion member are improved.
The cushion manufacturing apparatus of the invention may further comprise a secondary forming mold for holding the cushion member from both sides thereof and additionally forming the cushion member while the temperature of the cushion member, delivered continuously from the guide means, is within a range for thermal deformation. The secondary forming mold used may be a simple mold such as a punching metal mold having a large number of through holes. According to this manufacturing apparatus, the cushion member that is continuously delivered from the guide means can be accurately finished into the product shape by means of the secondary forming mold.
In the cushion manufacturing apparatus of the invention, the nozzle portion may include masking means for covering some of the nozzles so that the resin is discharged into a region inside the shaping guide surfaces of the guide means. With use of the nozzle portion constructed in this manner, the distribution of the continuous filaments that are discharged from the nozzles can be made to resemble the profile of the cushion member to be shaped by means of the guide means. Thus, according to this manufacturing apparatus, the shaping effect of the guide means can be further improved. The masking means may be provided with movable masking members that can change the discharge region of the nozzle portion.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.